1. Field
This disclosure relates generally to wireless communications systems, and more specifically, to methods and apparatus for decoding information in wireless communication systems.
2. Related Art
A wireless communication system includes a transmitting device and a receiving device. The transmitting device encodes data into bursts of coded bits. The bursts of coded bits are interleaved into a logical channel according to an interleaving scheme. For example, if the wireless network is an Enhanced General Packet Radio Service Network (E-GPRS) network or an Enhanced Data Rates for GSM Evolution (EDGE) network, the logical channel may include four bursts of coded bits. The logical channel is modulated and transmitted to the receiving device.
The receiving device receives the logical channel and demodulates each burst of coded bits independently. When demodulated, the bursts of coded bits are stored in contiguous memory partitions. Each burst of the logical channel must be of the same modulation type and therefore must include the same number of coded bits. However, in some situations, each burst of the logical channel received does not have the same modulation type as shown in FIG. 1A due to noise or other corruption for example.
In this example, a contiguous memory partition 100 includes four bursts of coded bits 102, 104, 106, and 108. Bursts 102, 106, and 108 are detected by the receiving device as being modulated using GMSK while burst 104 is detected as being modulated using 8PSK. The receiving device determines which modulation type was used by the transmitting device to modulate the logical channel. The receiving device determines the modulation type by a majority vote of the bursts of coded bits received. For example, if three bursts are of a first modulation type and one burst is of a second modulation type, the receiving device determines that the modulation type is the first modulation type. Therefore, in this example, the receiving device determines the modulation type to be GMSK.
The bursts of coded bits having a different modulation type (e.g. burst 104) than the majority (e.g., bursts 102, 106, and 108) are then overwritten in system memory with zero confidence information corresponding to the majority modulation type as shown in FIG. 1B. Since the majority modulation type in this example is GMSK, burst 104 is overwritten with 116 zero confidence bits. In addition, since each modulation type includes a different amount of information (e.g., a GMSK modulated burst includes 116 coded bits and an 8PSK modulated burst includes 348 coded bits), the receiving device adjusts the memory location of each burst of coded bits so that they are contiguous in system memory as shown in FIG. 1B.
Overwriting the burst of coded bits having a different modulation type and adjusting the memory location of each of the burst of coded bits consumes valuable system resources and time, which is undesirable. Therefore, it would be desirable, among other things, to provide for a more efficient and streamlined method of decoding bursts of coded bits that have multiple modulation types (e.g., detected or having been modulated using one of a plurality of different modulation schemes).